1. Field of the Invention
The present invention relates to a laser condensing optical system which condenses laser light in different sections of a medium.
This invention also relates to an optical system in which the position of a light source can be changed while ensuring that the intensity and the intensity distribution of light which is incident on a pupil face of the optical system remain constant. This invention particularly relates to an optical system which is ideal for condensing light in sections of a medium with different depths, or an optical system which is suitable for changing the condensing position.
2. Description of the Related Art
Conventionally, although there are demands to condense light in sections of different depths in a medium, spherical aberration tends to be generated in such cases. For example, in the field of biology, microscopic samples are generally prepared using glass-covered samples, in which a specimen is placed on a glass slide and sealed with a glass cover; spherical aberration is generated when specimens with glass covers of different thicknesses are observed through a microscope. Glass for LCD has different thicknesses, and spherical aberration may be generated when observing via a substrate. When the amount of spherical aberration varies between different thicknesses (depths), there is a problem of change (degradation) in the condensing performance.
Accordingly, various conventional techniques are used to condense light in sections of different thicknesses such as those mentioned above while correcting spherical aberration and suppressing change in the condensing performance.
For example, in one such technique, parallel plate glasses of different thicknesses are removably attached at the tip of a condensing optical system such as an objective lens.
There is also a conventional objective lens with a correction ring for microscope which successfully corrects aberration over an ultra-wide field, having a magnification of approximately 40-power and an NA (numerical aperture) of 0.93 (e.g. see Japanese Unexamined Patent Application, First Publication No. H05-119263 (FIG. 1 etc.)).
There is also an optical system which corrects spherical aberration by moving a spherical aberration correcting optical system of a combination focal length no power lens in the optical axis direction (e.g. see Japanese Unexamined Patent Application, First Publication No. 2003-175497 (FIG. 1 etc.)).
Furthermore, FIG. 32 shows a microscope device in which spherical aberration is corrected by arranging a spherical aberration correcting lens 252 between an objective lens 250 and a light source 251, and moving the spherical aberration correcting lens 252 along the optical axis (e.g. see Japanese Unexamined Patent Application, First Publication No. 2001-83428 (FIG. 1 etc.)).